As a technique to deposit thin films in a semiconductor manufacturing process, there is atomic layer deposition (hereinafter, ALD). In this ALD, gas is supplied in small amounts. For accurate supply of such small amounts of gas, it is necessary to stabilize a Cv value or factor.
In the ALD, for example, a high-temperature gas at about 200° C., such as liquefied titanium (a boiling point: 160° C.), is supplied. For resistance to the high-temperature gas, therefore, a metal diaphragm made of nickel-cobalt alloy having a thickness of 0.1 mm is used. However, when moved by the stem, the metal diaphragm having a thin plate-like shape exhibits unstable behavior and thus the Cv value becomes unstable. This is conceivable because the metal diaphragm will abruptly change at a certain point of time due to metal characteristics of the metal diaphragm.
The stability of the Cv value has been demanded in the ALD, whereas a problem occurs that the Cv value becomes unstable during supply of high-temperature gas. Therefore, there has been a demand for a diaphragm fluid control valve with a Cv value whose rate of variation or change is small even during supply of high-temperature gas. A technique for such a fluid control valve having a Cv value with a small variation rate during supply of high-temperature gas is disclosed in Patent Document 1 whose application was filed by the present applicant. A fluid control valve 100 shown in FIG. 10 is configured to adjust the stroke of a diaphragm in order to reduce the variation rate of the Cv value during supply of high-temperature gas. In this fluid control valve 100, the variation rate of the Cv value is ±10%.